Лако-красочные материалы — производство

As touched on previously, it is seemingly impossible to predict
accurately, in the few short weeks or months of the average product- development process, the chemical and physical changes that might occur after anything up to several years of storage on a consumer’s bathroom shelf, or in the dusty corner of a drug store in Timbuktoo. Similarly, the extremes of temperature and/or humidity that a product can be exposed to during transportation or sitting on a quayside in certain parts of the world can be severe, even if only for relatively short periods. Thus, over the years, accelerated test protocols have been developed to provide the manufacturer with a way of predicting likely shelf-life (which is normally a minimum of 2 years) and identifying potential problems before the product reaches the marketplace. The applications chemist has adapted these protocols to highlight any undesirable chemical or physical changes related to the fragrance. Thus, before submission to Business Scents Ltd, the leading contenders for the ‘Eve’ fragrance and its line extension modifications are sub­mitted to a battery of stability tests, as alluded to previously.

The Arrhenius rate equation forms the basis for the theory behind this accelerated testing. This states that for every 10 °С increase in tempera­ture, the rate of reaction doubles. Thus, in theory, the following applies:

12 months at 20 °С = 12 weeks at 40 °С = 6 weeks at 50 °С = 3 weeks at 60 °С

In practice, perfumery companies test all products at 0-4 °С, 20 or 25 °С and 37 °С (or 40 °С) for 12 weeks as a minimum standard. In addition, tests at 45 or 50 °С may be used (except for aerosols, which could explode) if quick results are required, or if it is likely that the product will experience these sort of conditions during its life-cycle. Stability for 4 weeks at 50 °С is considered acceptable in many instances, but signs of instability should be taken as precautionary only, particularly if the samples still appear satisfactory at 37 or 40 °С. This is because certain chemical reactions could occur at these high temperatures that could not happen at ambient temperatures or even at 37 °С. Note that 37 °С has become an accepted standard because many cosmetic chemists believe there is a temperature ‘barrier’, correspond­ing to the heat of the human body, above which chemical reactions are accelerated beyond that predicted by the Arrhenius equation.